It is built for one job: adding, subtracting, multiplying and dividing feet-inch-fraction dimensions on a tablet sitting on a bench, all day, without scrolling or squinting. Every answer on the tape shows the arithmetic that produced it, so you can check it the way you would check a hand calc.
FT for feet. Digits, then IN for inches./, denominator — 7 / 16. Any denominator up to 128.12 FT 5 IN 7 / 16 reads as 12'-5 7/16".12 . 4531 FT.FT or IN is read as inches when you add or subtract, and
as a plain multiplier when you multiply or divide. The tape says which reading it used, every time.Every value is carried as an exact fraction, not a decimal. 1/3 of 10'-0" is held as exactly 40", and ten thousand additions of 1/16" is exactly 52'-1" — there is no drifting decimal underneath. Only the big number on the screen is rounded, to the precision you picked in the top bar (1/8 through 1/128, default 1/16). When the displayed answer is not the exact answer, the tape prints the exact value and how far the rounding moved it. Rounding is to the nearest tick, halves away from zero.
| You do | You get |
|---|---|
| length + length, length − length | a length |
| length × plain number | a length (10 pieces at 3'-4 1/2") |
| length ÷ plain number | a length (a bay split into 7) |
| length ÷ length | a plain ratio, plus how many whole spaces fit and what is left over |
| length × length | refused. Two lengths multiplied is an area, and this calculator returns lengths. It tells you so instead of guessing. |
| anything ÷ 0 | refused, with the reason on the tape |
Key the feet, then FT; the inches, then IN; then the numerator, the fraction bar and the denominator. Every value is carried as an exact fraction rather than a decimal, so a long run of additions does not drift underneath you, and the tape prints the arithmetic behind each answer the way you would check a hand calc. Worked on this page's tape: 12'-5 7/16" + 3'-9 1/2", carried in sixteenths as 2391 + 728 = 3119, is 194.9375" = 16'-2 15/16" — exact at 1/16.
A bare number is read as inches when you add or subtract it, and as a plain multiplier when you multiply or divide by it. The tape says which reading it used, every time, so the assumption is on the paper rather than in the machine.
No, and the page refuses instead of guessing. Two lengths multiplied is an area, and this calculator returns lengths — it will not hand you a number whose units it cannot name. A length times a plain number, or a length divided by a plain number, both give a length; a length divided by a length gives a plain ratio, plus how many whole spaces fit and what is left over.
Whichever one you pick in the top bar, from an eighth to a hundred-and-twenty-eighth, with sixteenths as the default. The arithmetic underneath is exact and only the displayed answer is rounded — to the nearest tick, halves away from zero — and when the shown value is not the exact value the tape prints the exact one and how far the rounding moved it.
The fastest check: enter 12 FT 5 IN 7 / 16 + 3 FT 9 IN 1 / 2 =. The tape should show 2391 sixteenths
plus 728 sixteenths = 3119 sixteenths, and the answer 16'-2 15/16". If the tape's arithmetic and the big number
ever disagree, trust neither and tell us.
0-9 digits · . decimal · / fraction bar · f feet ·
i inches · + - * add, subtract, multiply ·
? or : divide (/ is the fraction bar, so divide needs its own key) ·
Enter equals · Backspace · Esc clear.